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We recently described general principles for designing ideal protein structures stabilized by completely consistent local and nonlocal interactions. The principles relate secondary structure patterns to tertiary packing motifs and enable design of different protein topologies. To achieve fine control over protein shape and size within a particular topology, we have extended the design rules by systematically analyzing the codependencies between the lengths and packing geometry of successive secondary structure elements and the backbone torsion angles of the loop linking them. We demonstrate the control afforded by the resulting extended rule set by designing a series of proteins with the same fold but considerable variation in secondary structure length, loop geometry, β-strand registry, and overall shape. Solution NMR structures of four designed proteins for two different folds show that protein shape and size can be precisely controlled within a given protein fold. These extended design principles provide the foundation for custom design of protein structures performing desired functions.

Small heat shock proteins (sHSPs) are nature’s ‘first responders’ to cellular stress, interacting with affected proteins to prevent their aggregation. Little is known about sHSP structure beyond its structured α-crystallin domain (ACD), which is flanked by disordered regions. In the human sHSP HSPB1, the disordered N-terminal region (NTR) represents nearly 50% of the sequence. Here, we present a hybrid approach involving NMR, hydrogen-deuterium exchange mass spectrometry, and modeling to provide the first residue-level characterization of the NTR. The results support a model in which multiple grooves on the ACD interact with specific NTR regions, creating an ensemble of ‘quasi-ordered’ NTR states that can give rise to the known heterogeneity and plasticity of HSPB1. Phosphorylation-dependent interactions inform a mechanism by which HSPB1 is activated under stress conditions. Additionally, we examine the effects of disease-associated NTR mutations on HSPB1 structure and dynamics, leveraging our emerging structural insights.

The holdase activity and oligomeric propensity of human small heat shock proteins (sHSPs) are regulated by environmental factors. However, atomic-level details are lacking for the mechanisms by which stressors alter sHSP responses. We previously demonstrated that regulation of HSPB5 is mediated by a single conserved histidine over a physiologically relevant pH range of 6.5—7.5. Here, we demonstrate that HSPB1 responds to pH via a similar mechanism through pHdependent structural changes that are induced via protonation of the structurally analogous histidine. Results presented here show that acquisition of a positive charge, either by protonation of His 124 or its substitution by lysine, reduces the stability of the dimer interface of the α-crystallin domain, increases oligomeric size, and modestly increases chaperone activity. Our results suggest a conserved mechanism of pH-dependent structural regulation among the human sHSPs that possess the conserved histidine, although the functional consequences of the structural modulations vary for different sHSPs.

Small heat shock proteins (sHSP) are a class of ATP-independent protein chaperones found throughout nature. They share a common ability to maintain partly unfolded proteins in soluble states under cellular stress conditions. All sHSPs contain a central domain called the α-crystallin domain (ACD); the domain is found in all sHSPs and in no other proteins and therefore defines the family. Though most sHSPs form large, often polydisperse oligomers from varying numbers of subunits, the ACD is both necessary and sufficient for formation of a dimer, the fundamental building block for oligomers. HSPB1 (also known as Hsp27) is unique among the ten human sHSPs because it contains a Cys residue in its dimer interface. HSPB1 is highly expressed under conditions of oxidative stress and is proposed to serve as a redox-sensitive chaperone. HSPB1 residue Cys137 has been proposed to modulate function by existing in either its oxidized (disulfide) or reduced (thiol) form (Chalova et al 2014). Here we report the solution-state NMR structure of oxidized HSPB1-ACD and compare it to a previously determined crystal structure of the reduced state. Formation of the disulfide-bond across the dimer interface yields a locked dimer structure with increased accessible hydrophobic surface. In the context of full-length HSPB1 oligomers, oxidation of Cys137 is associated with enhanced ability to bind the hydrophobic dye, 8-Anilinonapthalene-1-sulfonic-acid, implying an increased ability to interact with client proteins under oxidative stress.

Small heat shock proteins (sHSPs) comprise a class of ATP-independent chaperones that prevent aggregation of destabilized proteins in the cell. The structural mechanisms by which sHSPs complete their function remain enigmatic due to inherent properties that make them refractory to traditional approaches in structural biology. While sHSP monomers are small (on average 20 kDa), for certain sHSPs these monomers assemble into large homo-oligomers (~500 kDa) of variable size and shape. Structural heterogeneity is observed not only on a global scale but also at the local level. Observed heterogeneity is thought to stem from the predominantly disordered N-terminal region (NTR) of sHSPs. There is evidence for numerous sites on sHSPs for interacting with client proteins, although these interactions are often transient. The combination of transient interactions with clients, competing sHSP-client and sHSP-sHSP interactions, and presentation of different binding sites in variable states of an oligomer make it particularly challenging to understand structure-function relationships in sHSPs. The work presented in this thesis correlates local and global structural properties of the polydisperse human sHSP HSPB1. Hydrogen-deuterium exchange mass spectrometry (HDXMS) was used to identify solvent protected regions in the NTR of HSPB1 oligomers, providing the first full look at the NTR of an oligomeric human sHSP. Additionally, specific regions of local structural heterogeneity were identified in the NTR. Utilizing known mutations that perturb inter-protomer interactions in oligomers, a dimeric, full-length form of HSPB1 was obtained to represent a dispersed subunit of the system. The dimeric form of HSPB1 shows altered local structure in the NTR by HDXMS relative to WT oligomers, indicating distinct structural changes among different states of HSPB1. The dimeric construct is also amenable to traditional NMR approaches, allowing for development of a comprehensive model of full-length HSPB1 dimers, which still show structural heterogeneity. Disease-associated mutations in the NTR of HSPB1 were also characterized using HDXMS and a suite of other biophysical techniques. Specific regions in the NTR have altered protection among these disease mutants. These disease mutations were introduced to the dimeric construct to probe each mutation’s effect on oligomerization propensity. Interestingly, two of the disease mutations promote oligomerization while the other two disease mutations retain some dimer-like characteristics in the dimer-mutant context. HDXMS analysis of the disease mutants in the dimeric construct reveals distinct local structural effects for each mutant. It is most remarkable that mutations in the same region of HSPB1 have different local mechanistic effects, and that the subsequent global effects on oligomeric size or chaperone activity can appear similar for certain mutants. The methods explored in this thesis for characterizing heterogeneous structure in HSPB1 can be implemented to other sHSPs and similarly complex protein systems.

Small heat shock proteins (sHPSs) are nature's first responders to cellular stress, interacting with affected proteins to prevent their aggregation. Little is known about sHSP structure beyond its structured α-crystallin domain (ACD), which is flanked by disordered regions. In the human sHSP HSPB1, the disordered N-terminal region (NTR) represents nearly 50% of the sequence. Here, we present a hybrid approach involving NMR, hydrogen-deuterium exchange mass spectrometry, and modeling to provide the first residue-level characterization of the NTR. The results support a model in which multiple grooves on the ACD interact with specific NTR regions, creating an ensemble of quasi-ordered NTR states that can give rise to the known heterogeneity and plasticity of HSPB1. Phosphorylation-dependent interactions inform a mechanism by which HSPB1 is activated under stress conditions. Additionally, we examine the effects of disease-associated NTR mutations on HSPB1 structure and dynamics, leveraging our emerging structural insights.

This report describes the epidemiology and clinical course of patients younger than 21 years of age from 26 states who had multisystem inflammatory syndrome. Many were infected with SARS-CoV-2 at least 1 to 2 weeks before syndrome onset. The median age of the patients was 8.3 years, and 73% were previously healthy.

Multisystem inflammatory syndrome in children (MIS-C) is associated with recent or current SARS-CoV-2 infection. Information on MIS-C incidence is limited. To estimate population-based MIS-C incidence per 1 000 000 person-months and to estimate MIS-C incidence per 1 000 000 SARS-CoV-2 infections in persons younger than 21 years. This cohort study used enhanced surveillance data to identify persons with MIS-C during April to June 2020, in 7 jurisdictions reporting to both the Centers for Disease Control and Prevention national surveillance and to Overcoming COVID-19, a multicenter MIS-C study. Denominators for population-based estimates were derived from census estimates; denominators for incidence per 1 000 000 SARS-CoV-2 infections were estimated by applying published age- and month-specific multipliers accounting for underdetection of reported COVID-19 case counts. Jurisdictions included Connecticut, Georgia, Massachusetts, Michigan, New Jersey, New York (excluding New York City), and Pennsylvania. Data analyses were conducted from August to December 2020. Race/ethnicity, sex, and age group (ie, ≤5, 6-10, 11-15, and 16-20 years). Overall and stratum-specific adjusted estimated MIS-C incidence per 1 000 000 person-months and per 1 000 000 SARS-CoV-2 infections. In the 7 jurisdictions examined, 248 persons with MIS-C were reported (median [interquartile range] age, 8 [4-13] years; 133 [53.6%] male; 96 persons [38.7%] were Hispanic or Latino; 75 persons [30.2%] were Black). The incidence of MIS-C per 1 000 000 person-months was 5.1 (95% CI, 4.5-5.8) persons. Compared with White persons, incidence per 1 000 000 person-months was higher among Black persons (adjusted incidence rate ratio [aIRR], 9.26 [95% CI, 6.15-13.93]), Hispanic or Latino persons (aIRR, 8.92 [95% CI, 6.00-13.26]), and Asian or Pacific Islander (aIRR, 2.94 [95% CI, 1.49-5.82]) persons. MIS-C incidence per 1 000 000 SARS-CoV-2 infections was 316 (95% CI, 278-357) persons and was higher among Black (aIRR, 5.62 [95% CI, 3.68-8.60]), Hispanic or Latino (aIRR, 4.26 [95% CI, 2.85-6.38]), and Asian or Pacific Islander persons (aIRR, 2.88 [95% CI, 1.42-5.83]) compared with White persons. For both analyses, incidence was highest among children aged 5 years or younger (4.9 [95% CI, 3.7-6.6] children per 1 000 000 person-months) and children aged 6 to 10 years (6.3 [95% CI, 4.8-8.3] children per 1 000 000 person-months). In this cohort study, MIS-C was a rare complication associated with SARS-CoV-2 infection. Estimates for population-based incidence and incidence among persons with infection were higher among Black, Hispanic or Latino, and Asian or Pacific Islander persons. Further study is needed to understand variability by race/ethnicity and age group.

Summary We investigated the safety and efficacy of 90 mg/m 2 bendamustine HCL, administered intravenously on days 1 and 2 every 28 days in 10 women with platinum and taxane resistant epithelial ovarian cancer. There were no objective tumor responses observed; 2 patients had stable disease. Plasma samples collected at pre-treatment and end of cycle one were analyzed for changes in circulating total cytokeratin 18 and caspase cleaved cytokeratin 18 as exploratory early biomarkers of bendamustine-induced tumor cell death. All patients had measureable levels of both total and cleaved caspase 3 cytokeratin 18, but no relationship with response was possible due to the lack of clinical benefit in treated patients. Due to the high incidence of adverse events and absence of objective responses, only ten patients were treated as predefined by the Simon Two-Stage Design in the protocol. Overall, the regimen was not well tolerated and was associated with fatigue and a greater number of gastrointestinal side effects as compared to previously reported experiences in different patient populations. However, our study subjects did experience less bone marrow suppression. The lack of tolerability could reflect the degree of tumor burden within the peritoneal cavity as well as the high number of prior regimens (median of 5) received by the patients participating in this study.